Aluminum anodizing process and product thereof



United States Patent ALUMINUM ANODIZING PROCESS AND PRODUCT THEREOF Eugene Wainer, Shaker Heights, Ohio, assignor to Horizons Incorporated, a corporation of New Jersey No Drawing. Filed Sept. 7, 1965, Ser. No. 485,629

3 Claims. (Cl. 204-35) ABSTRACT OF THE DISCLOSURE Aluminum is anodized in a 1% sulfuric acid electrolyte, then dipped in deionized water and then in oxalic acid to produce a semi-white porcelain-like appearance in the product.

This invention relates to the anodizing of aluminum and aluminum base alloys and more particularly to procedures which result in a semi-white porcelain like surface appearance when the anodized material is sealed in the usual way.

Anodizing of aluminum and aluminum base alloys for the purpose of forming an absorbent oxide or hydrated oxide layer on such materials is old and well known and may be accomplished by a variety of techniques which may be either chemical or electrochemical, e.g. as described in United States Patent 1,946,150 and in the text Finishing of Aluminum" by Wernick and Pinner, published 1959.

The anodizing process of the present invention includes the following:

Preparation of a 1% sulfuric acid electrolyte by adding 1 gram of 98% H 50 to 99 cc. of H 0; and

Utilization of the electrolyte at temperatures between 45 C. and 55 C., voltages between 20 and 25 volts and current densities of between about 16 and 18 amperes per square foot for between about 20 and 30 minutes in order to obtain a thickness of between 0.2 and 1.2 mils of anodized surface and preferably 0.4 mil of such layer.

Vigorous air agitation is used throughout the anodizing procedure. The plate is removed from the hot anodizing bath, rinsed once in deionized water maintained at 50 C., and then immersed in a 3 percent solution of oxalic acid in deionized water for a period of minutes at 50 C. using air agitation or mechanical agitation during such immersion. After washing it in hot water and allowing it to dry, the aluminum foil so anodized is found to be an excellent receptor for the diffusion transfer process described in United States patent application. Ser. No. 485,627, filed concurrently herewith.

The invention will be better understood from the following example of a preferred embodiment thereof.

A sheet of 2S aluminum is anodized at 50 C. in the 1% sulfuric acid bath described above, using a voltage in the range of to volts, a current density in the range of 16 to 18 amperes per square foot, for a time period of 25 minutes. Vigorous air agitation is used throughout the anodizing procedure. The plate is removed from the hot anodizing bath, rinsed once in deionized water maintained at 50 C., and then immersed in a 3 percent solution of oxalic acid in deionized water for a period of 10 minutes at 50 C. using air agitation or mechanical agitation during such immersion. After washing it in hot water and allowing it to dry, the aluminum foil so anodized is found to be an excellent receptor for the diffusion transfer process.

3,411,994 Patented Nov. 19, 1968 The process is applicable to pure A1 as well as to alloys of which the aluminum comprises at least including alloys consisting of aluminum and between 1% and 4% of at least one metal selected from the group consisting of Ti, Ta, Zr, Nb, and Th or alloys consisting of aluminum and between 0.01% and 0.1% of a precious metal selected from the group consisting of Au, Ag, Pt or Pd, or alloys of aluminum containing the stated amounts of metals from both of said groups.

The surface resulting from the process is an excellent receptor for image forming materials, writing or ornamentation of the nature described in United States Patents 2,766,119, 2,115,339, and 3,108,932 and others of like nature.

The anodized surfaces produced by the process described are preferably sealed by immersion in a boiling solution of water containing 0.5% nickel acetate, 0.5% cobalt acetate and 1% boric acid and retention therein for 5 minutes.

The resulting product has a pleasing permanent semiwhite porcelain appearance.

I claim:

1. A process for anodizing aluminum and aluminum base alloy objects to produce an anodized product which is particularly suited to be used as a receptor for a photosensitive composition in diffusion transfer photography, which process comprises:

preparing an aqueous electrolyte consisting of 1% solution of sulfuric acid in water;

immersing said object to be anodized in said electrolyte; maintaining said electrolyte at a temperature between about 45 to 55 C.

anodizing the object at a voltage between 20 and 25 volts and a current density of between 16 and 18 amperes per square foot for between 20 and 30 minutes while the object is immersed in said electrolyte;

agitating said electrolyte during said anodizing step;

thereafter removing said object from said electrolyte;

then rinsing the object in warm deionized water; and

thereafter immersing the rinsed object in a solution of oxalic acid in deionized water for about 10 minutes while said solution is maintained at about 50 C.

2. The process of claim 1 wherein said oxalic solution is maintained agitated while said object is immersed therein.

3. The anodized object produced by the process of claim 1.

References Cited UNITED STATES PATENTS 1,965,683 7/1934 Work 204-42 2,107,318 2/1938 Work et a1. 204-58 XR 2,115,339 4/1938 Mason.

2,407,809 9/1946 Blackmun 204-35 XR 2,665,243 1/1954 Young et al. 204-3S 3,227,639 1/ 1966 Kampert 204-58 3,321,385 5/1967 Fazzari 204-35 OTHER REFERENCES Journal of the Electro Depositors Society, vol. 14, pp. -196, 193 8.

HOWARD S. WILLIAMS, Primary Examiner.

G. KAPLAN, Assistant Examiner. 

